Lisa Kudrow
Lisa Kudrow used to play free-spirited Phoebe in “Friends.” In this photo, the actress poses backstage with her award for TV Performance of the Year for “The Comeback” at the People Magazine Awards in Beverly Hills, California on Dec. 18, 2014. Reuters/Danny Moloshok

“Friends” had a lot of fantastic guest stars, including Brad Pitt, Sean Penn, Ben Stiller and Susan Sarandon. However, Lisa Kudrow recently said during an appearance on “Watch What Happens Live with Andy Cohen” that there was one particular guest star who was very rude to her.

“The worst behavior, off the top of my head?” she said, after a fan wanted to know about the worst behavior she encountered from a guest star. “I rehearsed without makeup most of the week, and then on show night, I’m in hair and makeup,” she recalled, before adding that this guest only deemed her attractive when she was all dolled up.

Kudrow did not reveal who that guest star was, but many speculated that it had to be Charlie Sheen. Several others guessed it might be Alec Baldwin or Bruce Willis, and one even said it had to be Penn.

When asked if Kudrow retaliated after the mean comment, she said that she told Matt LeBlanc, who plays Joey Tribiani in the series. “He’s like a big brother,” she said.

All of them maintained a good friendship over the years, and Kudrow even shared with TODAY that they recently enjoyed a reunion dinner. “It was really fun. We had such a good time,” she said. “It was hilarious. We were laughing nonstop.”

Many are hoping that there would be a “Friends” reunion in the works, but Kudrow did not sound positive about it. “If we don’t tell you one’s coming and it doesn’t happen, you have no reason to be disappointed,” she said. “I’m managing expectations. I don’t see it happening…it would be fun.”

Aside from those already mentioned, some of the unforgettable “Friends” guest stars include Reese Witherspoon, Christina Applegate and Winona Ryder, according to Bustle.

Anna Faris, Jon Lovitz, Julia Roberts, Brooke Shields, Jane Lynch, George Clooney, Dakota Fanning, Selma Blair, Freddie Prinze Jr. and Greg Kinnear also made appearances on the series, among many others.